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Abstract:

A defect recognition procedure in prepreg materials (1) draws a first
transversal cross line (4b) at the beginning boundary (3b) of a defective
area (2) in a prepreg material (1). A second transversal cross line (4e)
at the end boundary (3e) of a defective area (2) is drawn as well. The
cross lines (4b, 4e) form an angle (α) with respect to the prepreg
material (1) motion direction (5).
Each transversal cross line (4b, 4e) delimiting the beginning and the end
of a defective area (2) has identification codes (Bi, Ei).

Claims:

1- A defect recognition procedure in prepreg materials (1) characterized
in drawing a first transversal cross line (4b) at the beginning boundary
(3b) of a defective area (2) in a prepreg material (1) and drawing a
second transversal cross line (4e) at the end boundary (3e) of a
defective area (2) in a prepreg material (1).

2- A defect recognition procedure in prepreg materials (1) according to
claim 1, wherein the cross lines (4b, 4e) form an angle (α) with
respect to the prepreg material (1) motion direction (5), and the angle
(α) varies from 45.degree. to 90.degree..

3- A defect recognition procedure in prepreg materials (1) according to
any preceding claim, wherein each first transversal cross line (4b)
delimiting the beginning (3b) of a defective area (2) has a first
identification code (Bi), and each second transversal cross line
(4e) delimiting the end (3e) of a defective area (2) has a second
identification code (Ei).

4- A defect recognition procedure in prepreg materials (1) according to
claim 3, wherein the first identification code (Bi) and the second
identification code (Ei) are linked by using alphanumeric
characters.

5- A defect recognition procedure in prepreg materials (1) according to
claim 3, wherein the first identification code (Bi) and the second
identification code (Ei) are linked by using graphic characters.

6- A defect recognition procedure in prepreg materials (1) according to
any preceding claim, wherein the lines (4b, 4e) are drawn with a non
pollutant material that does not contain fluorine, neither
polytetrafluoroetylene nor uncured silicone.

7- A defect recognition procedure in prepreg materials (1) according to
any preceding claim, wherein the transversal cross lines (4b, 4e) are
detected by a defect detector laser sensor integrated in a manufacturing
machine.

8- A defect recognition procedure in prepreg materials (1) according to
claim 7, wherein the defect detector laser measures the loss of gain
between a first signal sent by the laser (preset value) and the signal
that the laser receives (current value) when such first signal rebounds
against the composite material (1).

9- A defect recognition procedure in prepreg materials (1) according to
claim 8, wherein for detecting defective areas (2), the comparison
between the signal preset value and the signal current value determines
whether or not there are defectives areas (2), so: a) if the current
value is set below a certain reference (for instance 30) defective areas
(2) are not considered; or b) if the current value exceeds a certain
reference (for instance 100) defective areas (2) are considered and the
laser control generates a signal error, stopping the machine.

Description:

OBJECT OF THE INVENTION

[0001] This invention discloses a procedure for marking and detecting
defective areas in preimpregnated material (also called "prepreg"). It is
included in the technical field of composite material manufacturing,
especially for the aerospace industry.

PROBLEM TO BE SOLVED AND BACKGROUND OF THE INVENTION

[0002] Most modern aircraft and spacecraft are manufactured using
composite materials with carbon fibres. There are several techniques for
manufacturing composite materials, like Resin Transfer Moulding (RTM),
Vacuum Assisted Resin Transfer Moulding (VARTM), Resin Infusion Moulding
(RIM), Fiber Placement (FP), Automated Fiber Placement (AFP) or Automatic
Tape Lying (ATL). All these techniques are well known in the state of the
art.

[0003] Preimpregnated materials ("prepregs") are used in some of these
techniques. When manufacturing prepreg materials sometimes defects are
also created, so defective areas must be detected and registered. Prepreg
manufacturers include a reference of defective areas associated to each
prepreg roll. These defective areas can be controlled and scrapped when
laying up using an encoder; an encoder is a device which measures the
length of each prepreg material roll as it is being laid up. The prepreg
manufacturer includes a defective areas list with each roll, so through
the encoders' use it is possible to detect the proximity of a defective
area. However, sometimes encoders are imprecise due to the fact that
prepreg rolls may slip or encoders may reset; therefore, encoders'
information may be wrong and some potential defective areas may be laid
up on the part.

[0004] Current automatic tape laying machines include laser defect
detection systems based on shade contrast. Nevertheless, the fine
calibration of these defect detection systems is hardly achieved due to
reflections produced by the incident light against the resin of the
prepeg material. The system generates continuous false alarm situations
because of these reflections. That is the reason why they are not
accurate enough and are usually turned off.

[0005] This invention presents a system to overcome the mentioned
drawbacks, marking failures in prepreg rolls. The object of the invention
is to include transversal cross lines in the boundary of a defective area
in a prepreg material. These transversal lines are marked with a non
pollutant material having a chemical composition that do not contaminate
the prepreg material; therefore, the marked lines mean no change of the
technical features of the final product.

[0006] These marked lines allow detecting defective area in the prepreg
material, avoiding their use in the parts that are going to be
manufactured. The prepreg rolls having defective areas are cut and
scrapped before the prepreg material is laid up with the ATL machine (or
any other machine used during the manufacturing process). Therefore, a
cost reduction is achieved due to the fact that manufactured parts do not
include those defective areas, and the parts are not rejected when
passing quality control inspections.

[0007] The state of the art shows different devices and procedures for
manufacturing and supplying prepreg materials. Document WO 2008/120023 A1
discloses a method and apparatus for making thermoplastic prepregs with
specific fiber orientation. Document JP 2005246631 A reveals a method for
detecting different kinds of prepreg materials and apparatus thereof.
However, no evidence about a procedure to recognize defective areas in
prepreg materials according to the present invention has been found.

SUMMARY OF THE INVENTION

[0008] In order to achieve the objectives and to solve the aforementioned
drawbacks, the invention has developed a defect recognition procedure in
prepreg materials. The procedure is characterized by drawing a first
transversal cross line at the beginning boundary of a defective area in a
prepreg material, and drawing a second transversal cross line at the end
boundary of a defective area in a prepreg material.

[0009] The cross lines form an angle with respect to the prepreg material
motion direction; such angle varies from 45° to 90°.

[0010] Each first transversal cross line delimiting the beginning of a
defective area has a first identification code. Similarly, and each
second transversal cross line delimiting the end of a defective area has
a second identification code.

[0011] According to a first embodiment, the first identification code and
the second identification code are linked using alphanumeric characters.
In a second embodiment, the first identification code and the second
identification code are linked using graphic characters.

[0012] The lines are drawn with a non pollutant material that does not
contain fluorine, neither polytetrafluoroetylene nor uncured silicone.
Such lines are detected by a defect detector laser sensor integrated in a
manufacturing machine.

[0013] The defect detector laser measures the loss of gain between a first
signal sent by the laser (preset value) and the signal that the laser
receives (current value) when such first signal rebounds against the
composite material.

[0014] During the procedure, the comparison between the signal preset
value and the signal current value determines whether or not there are
defective areas, so: a) if the current value is set below a certain
reference (for instance 30) defective areas (2) are not considered; or,
b) if the current value exceeds a certain reference (for instance 100)
defective areas are considered and the laser control generates a signal
error, stopping the machine.

[0015] In order to facilitate a better understanding of this
specification, and being an integral part thereof, a series of figures in
which the object of the invention has been represented with an
illustrative and not limitative manner is attached.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will be better understood from reading the following
detailed description taken in conjunction with the drawings in which
similar reference numbers are used to designate similar elements, and in
wherein:

[0017] FIG. 1 is a general view of a prepreg roll with marks highlighting
defective areas at such prepreg roll.

[0018]FIG. 2 shows a top view of the prepreg roll, detailing those marks.

[0019]FIG. 3 is a general scheme of a prepreg manufacturing process,
including the defective areas marking.

[0020] A list of reference numbers used on the drawings is given
hereinafter: 1=prepreg material and roll where it is stored; 2=defective
area; 3=boundary of a defective area; 3b=beginning boundary; 3e=end
boundary; 4=transversal cross lines; 4b=transversal cross line at the
beginning boundary; 4e=transversal cross line at the end boundary;
5=prepreg material motion direction; 6=uni-directional dry fibres;
7=resin film; 8=fibre and resin heating; 9=fibre and resin compaction;
10=inspection and line marking; Bi=identification code at the
beginning of a defective area; Ei=identification code at the end of
a defective area.

DETAILED DESCRIPTION

[0021] A description of the invention based on the aforementioned figures
is made hereinafter.

[0022] FIG. 1 shows a prepreg material roll (1) that is used for
manufacturing a part; the prepreg roll (1) may feed the ATL machine or
another device well known in the state of the art for manufacturing
composite parts. The prepreg material (1) is moved in a motion direction
(5) to feed the machine (not represented) that manufactures the parts.
The prepreg material (1) might have several defective areas (2). These
defective areas (2) must be avoided when manufacturing the parts;
otherwise these parts will have to be rejected during the quality control
process, increasing the manufacturing cost. In order to detect the
defective areas (2), several transversal cross lines (4) are marked for
detecting these defective areas (2). Each defective area (2) is
surrounded by a first transversal cross line (4b) at the beginning of the
defective area (2), and by a second transversal cross line (4e) at the
end of the defective area (2). A more detailed illustration can be seen
in FIG. 2.

[0023]FIG. 2 shows a top view of the prepreg roll (1), detailing the
previous mentioned cross lines (4b, 4e). The defective areas (2) can be
detected by their boundaries (3), having a beginning boundary (3b) and an
end boundary (3e). The beginning boundary (3b) and the end boundary (3e)
have been considered according to the previous mentioned motion direction
(5), although other references could have been considered when defining
these boundaries (3, 3b, 3e).

[0024] The cross lines (4b, 4e) form an angle (α) with respect to
the prepreg material (1) motion direction (5). Experience has shown that
these lines (4b, 4e) must have some kind of inclination in order to
optimize their detecting properties; sensors detecting these lines (4b,
4e) achieve a maximum detection when the mentioned angle (α) values
vary from 45° to 90°.

[0025] Due to the fact that each defective area (2) detected in the
prepreg material (1) is marked with a first transversal cross line (4b)
and a second transversal cross line (4e), the total number of transversal
cross lines (4b, 4e) must be an even number; otherwise there will be some
defective areas (2) wrongly marked. In order to increase safety
conditions, each first transversal cross line (4b) delimiting the
beginning of a defective area (2) has a first identification code
(Bi). Equally, each second transversal cross line (4e) delimiting
the end of a defective area (2) has a second identification code
(Ei) as well. Both codes (Bi, Ei) are linked. There are
several linking options: one of them is to use a code with alphanumeric
characters. According to this option, the first defective area (2)
detected in a prepreg material (1) is marked using a first transversal
cross line (4b) having a code (B1); the second transversal cross
line (4e) delimiting the end of the first defective area (2) has a second
identification code (E1). Similarly the second defective area (2)
detected has an identification code (B2) for its first transversal
cross line (4b) delimiting the beginning of the second defective area
(2), and there is another identification code (E2) for the second
transversal cross line (4e) delimiting the end of the second defective
area (2) as well. Therefore, for N defective areas (2) detected in the
prepreg material (1) there are 2N identification codes: B1, E1,
B2, E2, B3, E3, . . . BN, EN.

[0026] A sensor (not shown) detects each identification code (Bi,
Ei) included at each transversal cross line (4b, 4e). The sensor
reads the first identification code (Bi) associated to a defective
area (2), and immediately it reads the second identification code
(Ei); in case of a malfunction when detecting any of these codes
(Bi, Ei) (i.e. that one of them has not been detected) an error
signal is produced, a message is shown in the machine control display and
the machine stops until the operator checks the roll and the lay up
process is resumed.

[0027] Other linking methods may be employed using graphic characters
instead of alphanumeric ones. This means that each identification code
(Bi, Ei) may be set up by graphic characters using geometric
shapes (like circles, triangles, squares, and other geometric figures and
their combinations). This embodiment has not been illustrated in the
figures.

[0028]FIG. 3 represents a general scheme of a prepreg material (1)
manufacturing process, including the marking of defective areas (2).
Uni-directional dry fibres (6) are mixed together with resin film (7).
Later on this mixture undergoes heating (8) and compaction (9) processes.
Finally the prepreg material (1) is inspected and marked (10) with cross
lines (4b, 4e) when defective areas (2) are detected. After the
inspection and marking process (10), the prepreg material (1) is stored
in rolls.

[0029] The cross lines (4b, 4e) are marked with a non pollutant material
that do not contaminate the prepreg material (1). Typical waste material
that can damage composite materials are fluorine, polytetrafluoroetylene
(PTFE, Teflon®) and uncured silicone waste; therefore, the marking
material cannot contain any of these substances.

[0030] The cross lines (4b, 4e) also have such optical characteristics of
refraction that enables the possibility to be detected with the standard
ATL machine defect detector laser. This defect detector laser measures
the loss of gain between a first signal sent by the laser (called preset
value) and the signal that the laser receives (current value) when such
first signal rebounds against the composite material (1). For detecting
defective areas (2), the comparison between the signal preset value and
the signal current value determines whether or not there are defectives
areas (2). If the current value is set below a certain reference (for
instance 30) defective areas (2) are not considered; nevertheless, if the
current value exceeds a certain reference (for instance 100) defective
areas (2) are considered and the laser control generates a signal error,
stopping the machine. Thus, the defective areas (2) are discarded
preventing them from being used in the manufacture of new parts.

Patent applications by Jose David Cano Cediel, Madrid ES

Patent applications by AIRBUS Operations S.L.

Patent applications in class INSPECTION OF FLAWS OR IMPURITIES

Patent applications in all subclasses INSPECTION OF FLAWS OR IMPURITIES